Expressed as Legnth x Width x Thickness
On residential slate roofing projects, 16" to 18" random width, 16" x 8" or 10", 18" x 12", and 20" x 10" constant width are the most common sizes.
On commercial slate roofing projects 16", 18" and 20" random are often seen, but 20" x 10" and 24" x 12" are more common on large formal projects.
The standard thickness of slate is 3/16" to 1/4" for smooth textured products and 1/4" to 3/8" for heavier textured stone. About 90% of all slate projects use standard thickness, but the other 10% can range from 3/16" all the way to 1". A "Graduate thickness" slate roof is an installation where the lower sections of the slate roof have "heavy" or extra thick slate and then the slate goes down in thickness as it progresses up toward the peak. These installations are somewhat more complicated but can provide a more dramatic texture on the slate roof. "Graduation" tends toward the more natural and is almost unseen in combination with constant width jobs.
Weight Consideration:
Most homes where slate is a consideration can support the weight of standard thickness slate roof with out mondification. Standard slate weighs about 8 lbs. per square foot, but varies with color and texture. In situations where the weight is too high, bracing of rafter spans is usually sime and relatively inexpensive. We can provide guidelines and recommend roof structure consultants to determine the feasibility. In the end it is "better to be safe than sorry" so if the house is not designed for the weight of "hard roof products", it should be investigated. |
